Battery pack system of improving operating performance using internal resistance of cell

ABSTRACT

Disclosed is a battery pack system to supply current necessary to operate an external device, including a battery module including battery cells which can be charged and discharged, a temperature sensor, an auxiliary power unit to supply a charge and discharge pulse current to the battery module, and a controller to connect the auxiliary power unit to the battery module so that the charge and discharge pulse current is supplied to the battery module when a measured temperature (T bat ) of the battery module is less than a set temperature (T crit ) based on information detected by the temperature sensor before the battery module is electrically connected to the external device and to interrupt the supply of the charge and discharge pulse current to the battery module when the temperature of the battery module becomes equal to or greater than the set temperature (T crit ) and an operating method of the same.

TECHNICAL FIELD

The present invention relates to a battery pack system with improvedoperating performance using internal resistance of a cell, and, moreparticularly, to a battery pack system to supply current necessary tooperate an external device, the battery pack system including a batterymodule including a plurality of battery cells which can be charged anddischarged, the battery module to supply power to the external device, atemperature sensor to detect the temperature of the battery module, anauxiliary power unit to supply a charge and discharge pulse current tothe battery module, and a controller to connect the auxiliary power unitto the battery module so that the charge and discharge pulse current issupplied to the battery module when a measured temperature (T_(bat)) ofthe battery module is less than a set temperature (T_(crit)) based oninformation detected by the temperature sensor before the battery moduleis electrically connected to the external device and to interrupt thesupply of the charge and discharge pulse current to the battery modulewhen the temperature of the battery module becomes equal to or greaterthan the set temperature (T_(crit)) and an operating method of the same.

BACKGROUND ART

Secondary batteries have attracted considerable attention as energysources for wireless mobile devices. In addition, secondary batterieshave attracted considerable attention as power sources for electricvehicles (EV), hybrid electric vehicles (HEV), and plug-in hybridelectric vehicles (Plug-in HEY), which have been developed to solveproblems, such as air pollution, caused by existing gasoline and dieselvehicles using fossil fuels.

Such electric vehicles, hybrid electric vehicles and plug-in hybridelectric vehicles are devices which must be operated under more harshconditions than small-sized mobile devices. That is, it is necessary forelectric vehicles, hybrid electric vehicles and plug-in hybrid electricvehicles to exhibit proper performance in summer, for example at hightemperature, and in winter, for example at low temperature.

To obtain good high temperature performance, a secondary battery havinghigh temperature safety has been manufactured or a method of forming acoolant channel in a battery module or a battery pack has been used.

At low temperature, on the other hand, the secondary battery exhibitslower efficiency than at high temperature because the internalresistance of the battery is high at low temperature. As a result, thecapacity of the battery is restricted and the liftspan of the battery isreduced.

In order to solve the above problems, a method of improving the lowtemperature performance of a battery has been studied. In such abattery, however, the low temperature performance of the battery isimproved but the capacity and the high temperature performance of thebattery are deteriorated.

As another method of improving low temperature performance of thebattery, a method of increasing the temperature of the battery using anadditional heating apparatus (heater) may be considered. However, muchtime is taken due to high thermal capacity of the battery, and thecapacity of the battery is reduced due to internal power consumption.

Consequently, there is a high necessity for a battery pack system thatis capable of minimizing internal power consumption while exhibitingexcellent performance at low temperature without change in batteryperformance.

DISCLOSURE Technical Problem

Therefore, the present invention has been made to solve the aboveproblems, and other technical problems that have yet to be resolved.

As a result of a variety of extensive and intensive studies andexperiments on a middle or large-sized battery pack case, the inventorsof the present application have found that, if an auxiliary power unitis connected to a battery module so that a charge and discharge pulsecurrent is supplied to the battery module when a measured temperature(T_(bat)) of the battery module is less than a set temperature(T_(crit)) based on information detected by a temperature sensor beforethe battery module is electrically connected to an external device,large internal resistance of the battery module serves as a heating bodyto increase the temperature of the battery module. The present inventionhas been completed based on these findings.

Technical Solution

In accordance with one aspect of the present invention, the above andother objects can be accomplished by the provision of a battery packsystem to supply current necessary to operate an external device, thebattery pack system including a battery module including a plurality ofbattery cells which can be charged and discharged, the battery module tosupply power to the external device, a temperature sensor to detect thetemperature of the battery module, an auxiliary power unit to supply acharge and discharge pulse current to the battery module, and acontroller to connect the auxiliary power unit to the battery module sothat the charge and discharge pulse current is supplied to the batterymodule when a measured temperature (T_(bat)) of the battery module isless than a set temperature (T_(crit)) based on information detected bythe temperature sensor before the battery module is electricallyconnected to the external device and to interrupt the supply of thecharge and discharge pulse current to the battery module when thetemperature of the battery module becomes equal to or greater than theset temperature (T_(crit)).

In the battery pack system according to the present invention, largeinternal resistance of the battery module is used as a kind of heatingbody to increase the temperature of the battery module at a settemperature, such as low temperature, due to the charge and dischargepulse current from the auxiliary power unit. Consequently, it ispossible to rapidly increase the temperature of the battery modulewithin a short time irrespective of the thermal capacity of the batteryunlike the conventional art at which an additional heating apparatus isused. Also, the capacity of the battery due to internal powerconsumption is not reduced. That is, the operating efficiency of thebattery module is greatly improved.

The battery pack system particularly constructed as described above ispreferably applicable to a case in which it is necessary to rapidlyincrease the temperature of the battery pack within a short time asneeded so that the operating efficiency of the battery pack is maximizedas well as a case in which it is necessary to increase the temperatureof the battery module when the temperature of the battery module is lowdue to external environmental factors so that the battery module canreach a properly operating state.

The kind of each of the battery cells constituting the battery module isnot particularly restricted so long as each of the battery cells is asecondary battery which can be charged and discharged. For example, eachof the battery cells may be a prismatic battery cell, a cylindricalbattery cell or a plate-shaped battery cell.

Generally, it is necessary for a battery pack to have high power outputand large capacity so as to be used as a power source for middle orlarge-sized devices. To this end, a plurality of small-sized secondarybatteries (unit cells) is connected in series and/or in parallel to eachother to constitute a battery module, and a plurality of battery modulesis connected in series and/or in parallel to each other to constitute abattery pack. For high integration, therefore, each of the battery cellsis preferably a plate-shaped secondary battery.

The structure of and material for the plate-shaped battery cell are notparticularly restricted. For example, the plate-shaped battery cell maybe a pouch-shaped battery cell having a structure in which an electrodeassembly having a cathode/separator/anode structure is mounted in abattery case formed of a laminate sheet comprising a resin layer and ametal layer.

For reference, the term ‘battery module’ as used in the specificationincludes the structure of a battery system configured to have astructure in which two or more chargeable and dischargeable batterycells or unit modules are mechanically coupled and, at the same time,electrically connected to each other so as to provide high-power,large-capacity electricity. Therefore, the battery module itself mayconstitute a single apparatus or a part of the large-sized apparatus.For example, a plurality of small-sized battery modules may be connectedto each other to constitute a large-sized battery module. Alternatively,a small number of battery cells may be connected to each other toconstitute a unit module, and a plurality of the unit modules may beconnected to each other.

Meanwhile, the unit module may be configured to have various structures,a preferred example of which will be described hereinafter.

The unit module is configured to have a structure in which a pluralityof plate-shaped battery cells, each of which has electrode terminalsformed at the upper and lower ends thereof, are connected in series toeach other. Specifically, the unit module may include two or morebattery cells arranged in a stacked structure in which connection partsbetween the electrode terminals of the battery cells are bent andhigh-strength cell covers coupled to each other to cover the exteriorsof the battery cells excluding the electrode terminals of the batterycells.

Two or more battery cells are covered by the high-strength cell coverswhich are made of synthetic resin or metal to constitute a unit module.The high-strength cell covers protect the battery cells, which have lowmechanical strength, and, in addition, restrain the change in repetitiveexpansion and contraction during charge and discharge of the batterycells, thereby preventing sealing portions of the battery cells frombeing separated from each other. Consequently, it is possible tomanufacture a battery module assembly exhibiting better safety.

The battery cells are connected in series and/or parallel to each otherin one unit module, or the battery cells of one unit module areconnected in series and/or parallel to the battery cells of another unitmodule. In a preferred example, a plurality of unit modules may bemanufactured by coupling electrode terminals of the battery cells toeach other, while arranging the battery cells in series in thelongitudinal direction, so that the electrode terminals of the batterycells are successively adjacent to each other, bending the battery cellsby twos or more so that the battery cells are stacked, and covering thestacked battery cells by predetermined numbers with the cell covers.

Coupling between the electrode terminals may be achieved in variousways, such as welding, soldering, and mechanical coupling. Preferably,coupling between the electrode terminals is achieved by welding.

A plurality of battery cells or unit modules, which is stacked in highintegration while electrode terminals of the battery cells or the unitmodules are connected to each other, may be vertically mounted inseparable upper and lower cases that are configured to be coupled toeach other in the assembly-type coupling structure to constitute arectangular battery module.

The details of a unit module and a rectangular battery modulemanufactured using a plurality of unit modules are disclosed in KoreanPatent Application No. 2006-45443 and No. 2006-45444, which have beenfiled in the name of the applicant of the present application and thedisclosure of which is incorporated herein by reference.

The connection between the battery module and the device may be achievedin various manners. For example, a switch may be located at theelectrical connection region between the battery module and the deviceso that the switch can be turned on or off according to a signal fromthe controller, to which, however, the present invention is not limited.

In the battery pack system according to the present invention, thetemperature of the battery module detected by the temperature sensor mayvary according to setting conditions. For example, the temperatures ofsome or all of the battery cells may be measured, and the highesttemperature and the lowest temperature may be set as the measuredtemperature (T_(bat)), the average of the measured temperatures may beset as the measured temperature (T_(bat)), or the temperature of thebattery cell(s) located at a specific position may be set as themeasured temperature (T_(bat)). The measured temperature (T_(bat)) isimportant information necessary for the controller to perform a seriesof procedures.

Generally, the internal resistance of a secondary battery increases asthe temperature of the secondary battery decreases. Referring to FIG. 1,the internal resistance of the secondary battery at a temperature of−10° C. is 4 times the internal resistance of the secondary battery at atemperature of 25° C. It is possible to raise the temperature of thesecondary battery at low temperature with high efficiency (I²*R) usingthe internal resistance of the secondary battery. If power is consumedduring raising of the temperature of the secondary battery based on theinternal resistance thereof, however, the discharge of the batterymodule to drive the external device may be accelerated.

On the other hand, the battery pack system according to the presentinvention includes the auxiliary power unit to supply the charge anddischarge pulse current to the battery module. Consequently, it ispossible to rapidly raise the temperature of the battery module to aproper temperature while minimizing power consumption in the batterymodule by virtue of the charge and discharge pulse current between thebattery module and the auxiliary power unit.

That is, charge and discharge between the battery module and theauxiliary power unit are continued to minimize power consumed throughpower circulation and to raise the temperature of the battery moduleusing heat generation due to the internal resistance during the chargeand discharge operation.

If the low temperature efficiency of the battery pack system is improvedas described above, an attempt may not be necessary to chemically changea cathode, an anode and an electrolyte of the existing battery, therebyimproving the low temperature efficiency of the battery pack system.Specifically, a method of chemically changing the battery to improve thelow temperature efficiency is not preferable in terms of the hightemperature performance, the capacity or the electrical efficiency. Inthe battery pack system according to the present invention, on the otherhand, it is possible to use a battery having advantages in terms of thehigh temperature performance, the capacity or the electrical efficiency,thereby providing a battery module having higher performance than theconventional battery module.

The kind of the auxiliary power unit of the battery pack system is notparticularly restricted so long as the auxiliary power unit is connectedto the battery module to supply the charge and discharge pulse currentto the battery module. In a preferred example, the auxiliary power unitmay be a low-capacity auxiliary battery or a capacitor.

In a case in which a low-capacity auxiliary battery is used as theauxiliary power unit, the capacity of the auxiliary battery ispreferably 3 to 15% that of the battery module. If the capacity of theauxiliary battery is greater than 15% that of the battery module, thesize of the battery pack system relative to the power of the batterymodule supplied to the external device increases with the result thatefficiency of the battery pack system is lowered. On the other hand, ifthe capacity of the auxiliary battery is less than 3% that of thebattery module, the operating time of the auxiliary power unit to raisethe temperature of the battery module increases, which is notpreferable. More preferably, the capacity of the auxiliary battery is 4to 12% that of the battery module.

The auxiliary power unit may be charged in various ways. For example,the auxiliary power unit may be charged by the battery module in a statein which the battery module is or is not electrically connected to theexternal device or may be charged by an additional power supply unit(for example, a battery to operate electronic components) of theexternal device, to which, however, the present invention is notlimited.

In consideration of the relationship between the temperature and theinternal resistance shown in FIG. 1, the set temperature (T_(crit)) tooperate the auxiliary power unit may be set to a temperature range of−5° C. to 10° C. based on properties of the unit cell. Preferably, theset temperature (T_(crit)) is set to a temperature range of −2° C. to10° C.

On the other hand, when the temperature of the battery pack is rapidlyraised within a short time as needed even at a temperature at which theoperation of the battery pack is properly performed so as to maximizethe operation efficiency of the battery pack, the set temperature(T_(crit)) may be higher than the temperature at which the operation ofthe battery pack is properly performed. For example, the set temperature(T_(crit)) may be 5° C. to 20° C. higher than a temperature of 15° C. to40° C. at which the operation is properly performed.

Consequently, the set temperature (T_(crit)) may be changed according tothe purpose of temperature raising. According to circumstances, thesystem may be set so as to include two or more set temperatures.

Meanwhile, in the battery pack system, the charge and discharge pulsecurrent is preferably a pulse wave current having the same charge anddischarge rate. In order to raise the temperature of the battery modulewhile minimizing power consumption of the battery module, the charge anddischarge rates of the charge and discharge pulse current must be thesame. In this state, loss of power in the battery module due to powercirculation is minimized

In this case, the pulse wave current may be, for example, a square wavetype pulse wave current or a sine wave type pulse wave current. In thepulse wave current, a (+) integral value and a (−) integral value ateach waveform becomes charge and discharge rates, and therefore, thecharge and discharge rates are the same.

The size and supply time of the charge and discharge pulse current maybe changed depending upon the capacity of the battery module, thecapacity of the auxiliary power source, the difference between themeasured temperature (T_(bat)) and the set temperature (T_(crit)) or thelike. In a preferred example, the charge and discharge pulse current maybe supplied at a ⅓ C-rate to 5 C-rate of each battery cell constitutingthe battery module for 2 to 30 seconds. Experiments performed by theinventors reveal that, in an exemplary battery pack system, time takento reach 10° C. from −30° C. varies according to C-rate conditions.

In the battery pack system, the controller serves to control theoperations of the respective components constituting the battery packsystem. For example, the controller may control pulse current inconsideration of the measured temperature and upper-limit C-rate at lowtemperature.

The application of the controller to the battery pack system is notparticularly restricted. For example, the controller may be anindependent apparatus or may be mounted in a battery management system(BMS).

In a preferred example, the battery pack system may further include abidirectional converter disposed between the battery module and theauxiliary power unit to supply the charge and discharge pulse current.

According to an operating signal from the controller, the bidirectionalconverter may supply the charge and discharge pulse current from theauxiliary power unit to the battery module or charge the auxiliary powerunit with current of the battery module.

In accordance with another aspect of the present invention, there isprovided a device including the battery pack system as a power source.

The device may be a power tool, which is operated with power from anelectric motor, an electric automobile, such as an electric vehicle(EV), a hybrid electric vehicle (REV) or a plug-in hybrid electricvehicle (PHEV), an electric two-wheeled vehicle, such as an electricbicycle (E-bike) or an electric scooter (E-scooter), or an electric golfcart, to which, however, the present invention is not limited.

Preferably, the device is an electric automobile, an electrictwo-wheeled vehicle or an electric golf cart, the performance of whichis required to be maintained at low temperature and/or temperature ofwhich is regulated as needed so as to maximize the operating efficiencythereof. More preferably, the device is an electric vehicle, a hybridelectric vehicle or a plug-in hybrid electric vehicle.

In accordance with a further aspect of the present invention, therefore,there is provided an operating method of the battery pack system asdescribed below.

Specifically, the operating method of the battery pack system includes(a) measuring the temperature of the battery module before the batterymodule is electrically connected to the external device, (b) connectingthe auxiliary power unit to the battery module so that the charge anddischarge pulse current is supplied to the battery module when themeasured temperature (T_(bat)) of the battery module is less than theset temperature (T_(crit)), (c) increasing the temperature of thebattery module according to the supply of the charge and discharge pulsecurrent to the battery module, (d) interrupting the supply of the chargeand discharge pulse current to the battery module when the temperatureof the battery module is equal to or greater than the set temperature(T_(crit)), and (e) electrically connecting the battery module to theexternal device.

According to circumstances, the operating method may further includecharging the auxiliary power unit before step (a) or step (b) or afterstep (e). As previously described, the auxiliary power unit may becharged by the battery module in a state in which the battery module iselectrically connected to the external device or is not electricallyconnected to the external device or may be charged by an additionalpower supply unit (for example, a battery to operate electroniccomponents) of the external device.

When the auxiliary power unit is charged using the battery to operateelectronic components, it is possible to reduce damage to the batterymodule, the performance of which is lowered at low temperature, and tocharge the auxiliary power unit even when the battery module is notsufficiently charged.

The operating method of the battery pack system according to the presentinvention may be performed immediately before the battery module isconnected to the external device to increase the temperature of thebattery module to a range of the set temperature (T_(crit)) within ashort time or while the temperature of the battery module continues tobe monitored, in a state in which the external device is stopped (OFF),to maintain the temperature of the battery module at the set temperature(T_(crit)) or more. In the latter case, it is possible to maintain thetemperature of the battery module within a usable range through chargeand discharge within a short time, thereby reducing wait time before thedevice can operate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a graph illustrating the change in internal resistance of asecondary battery according to temperature;

FIG. 2 is a graph illustrating the form of a square wave type pulse wavehaving the same charge and discharge rate;

FIG. 3 is a graph illustrating the form of a sine wave type pulse wavehaving the same charge and discharge rate;

FIG. 4 is a graph illustrating a temperature rise curve of a batterywhen a battery pack system according to an embodiment of the presentinvention is applied;

FIG. 5 is a typical construction view of a battery pack system accordingto an embodiment of the present invention; and

FIG. 6 is a flow chart illustrating a battery pack temperature controlmethod of a battery pack system according to an embodiment of thepresent invention.

BEST MODE

Now, preferred embodiments of the present invention will be described indetail with reference to the accompanying drawings. It should be noted,however, that the scope of the present invention is not limited by theillustrated embodiments.

FIG. 1 is a graph illustrating the change in internal resistance of asecondary battery according to temperature.

Referring to FIG. 1, the relative change in internal resistance of asecondary battery according to temperature is shown based on theinternal resistance of the secondary battery at a temperature of 25° C.As the temperature falls, the internal resistance gently increases. Theinternal resistance at a temperature of 10° C. is more than 1.5 timesthe internal resistance at a temperature of 25° C. Subsequently, theinternal resistance sharply increases. The internal resistance at atemperature of 0° C. is 2.5 times the internal resistance at atemperature of 25° C. The internal resistance at a temperature of −10°C. is 4 times the internal resistance at a temperature of 25° C.

Work with respect to the internal resistance of the battery becomesthermal energy generated during charge and discharge of the battery.That is, W=VI=I²R. Thermal energy W is proportional to internalresistance R. When the internal resistance increases at low temperature,therefore, thermal energy also increases.

FIGS. 2 and 3 are graphs illustrating forms of a pulse wave having thesame charge and discharge rate usable in the battery pack systemaccording to the present invention.

Referring to these drawings, integral values with respect to time ineach graph becomes charge and discharge capacities. When (+)/(−)integral values are the same, therefore, the charge and dischargecapacities are the same, thereby minimizing internal power consumptionof a battery module.

FIG. 4 is a graph illustrating a temperature rise curve of a batterywhen a battery pack system according to an embodiment of the presentinvention is applied.

Referring to FIG. 4, it can be seen that the inclination of the graphbecomes gentler with the progress of time. This is because internalresistance decreases as temperature increases, as previously described,and therefore, thermal energy decreases in proportion to the internalresistance.

Also, it can be seen that it takes approximately 250 seconds to increasethe temperature of the battery from −30° C. to 10° C. When the batteryis heated using an external heat supply unit, it is difficult to achievesuch a rapid increase in temperature within a short time due to highthermal capacity of the battery.

According to circumstances, if the battery module is configured so thatthe temperature of the battery module remains within a predeterminedrange through charge and discharge of the battery when the temperatureof the battery module continues to be monitored, in a state in which adevice is stopped, and a measured temperature T_(bat) is less than a settemperature T_(crit), the operating time of the battery pack system maybe very short, for example several seconds to several tens of seconds.

FIG. 5 is a typical construction view of a battery pack system accordingto an embodiment of the present invention

Referring to FIG. 5, a battery pack system 100 according to anembodiment of the present invention includes a battery module 300 tosupply power to an external device 200, a temperature sensor 310 tomeasure temperature of the battery module, an auxiliary power unit 400to supply a charge and discharge pulse wave current, a bidirectionalconverter 500 connected between the battery module 300 and the auxiliarypower unit 400, and a controller 600 to control the above components.

The battery module 300 is connected to or disconnected from a devicecontroller 210 by ON/OFF operation of a switch 110 to perform electricalswitching between the battery module 300 and the device 200 according toa signal from the controller 600.

In a state in which the switch 110 is OFF, the temperature of thebattery module is measured by the temperature sensor 310, and thecontroller 600 compares the measured temperature T_(bat) with the settemperature T_(crit).

When the measured temperature T_(bat) is less than the set temperatureT_(crit) as the result of the temperature comparison, the controller 600connects the auxiliary power unit 400 to the battery module 300 so thata charge and discharge pulse wave current is supplied to the batterymodule 300 via the bidirectional converter 500 disposed between thebattery module 300 and the auxiliary power unit 400. Upon the supply ofthe charge and discharge pulse wave current to the battery module 300,the temperature of the battery module 300 increases. As a result, whenthe temperature of the battery module 300 becomes equal to or greaterthan the set temperature T_(crit), the controller 600 electricallydisconnects the auxiliary power unit 400 from the battery module 300 andelectrically connects the battery module 300 to the device 200 via theswitch 110. Consequently, the temperature of the battery module 300increases to at least the set temperature T_(crit), before the batterymodule 300 is connected to the device 200, thereby maximizing theoperating efficiency of the battery pack system.

According to circumstances, the above operation may be repeatedlyperformed so that the temperature of the battery module 300 is kept atthe set temperature T_(crit) even in a state in which the connection ofthe battery module 300 to the device is not considered, whereby theconnection between the battery module 300 and the device 200 may bepossible at all times.

FIG. 6 is a flow chart illustrating a battery pack temperature controlmethod of a battery pack system according to an embodiment of thepresent invention.

Referring to FIG. 6 together with FIG. 5, the controller 600 reads a settemperature T_(crit) when the battery pack system 100 is operated(S100), and the temperature sensor 310 measures temperature T_(bat) ofthe battery module 300 (S110). Subsequently, the controller 600determines whether the measured temperature T_(bat) is less than the settemperature T_(crit) (S120). For example, the set temperature T_(crit)may be 0° C.

When it is determined that the measured temperature T_(bat) is less thanthe set temperature T_(crit) (YES), the controller 600 connects theauxiliary power unit 400 to the battery module 300 via the bidirectionalconverter 500 so that a charge and discharge pulse wave current issupplied to the battery module 300 (S130). On the other hand, when it isdetermined that the measured temperature T_(bat) is equal to or greaterthan the set temperature T_(crit) (NO), the controller 600 connects thebattery module 300 to the device 200 (S150).

At the step of supplying the charge and discharge pulse wave current(S130), the charge and discharge pulse wave current is supplied to thebattery module, and it is determined whether the measured temperatureT_(bat) of the battery module 300 is less than the set temperatureT_(crit). When it is determined that the measured temperature T_(bat) isless than the set temperature T_(crit) (YES), the procedure returns tothe step of supplying the charge and discharge pulse wave current (S130)so that the step of supplying the charge and discharge pulse wavecurrent and the subsequent step are performed. When it is determinedthat the measured temperature T_(bat) is equal to or greater than theset temperature T_(crit) (NO), the procedure advances to the step ofconnecting the battery module 300 to the device 200 (S150).

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

As is apparent from the above description, it is possible for thebattery pack system according to the present invention and the operatingmethod of the same to rapidly increase the temperature of the batterymodule to a usable range based on a heat generation phenomenon duringcharge and discharge of the battery due to high internal resistance at aset temperature while minimizing internal power consumption of thebattery module using the auxiliary power unit to supply a pulse wavecurrent to the battery module.

1. A battery pack system to supply current necessary to operate anexternal device, the battery pack system comprising: a battery modulecomprising a plurality of battery cells which can be charged anddischarged, the battery module to supply power to the external device; atemperature sensor to detect a temperature of the battery module; anauxiliary power unit to supply a charge and discharge pulse current tothe battery module; and a controller to connect the auxiliary power unitto the battery module so that the charge and discharge pulse current issupplied to the battery module when a measured temperature (T_(bat)) ofthe battery module is less than a set temperature (T_(crit)) based oninformation detected by the temperature sensor before the battery moduleis electrically connected to the external device and to interrupt thesupply of the charge and discharge pulse current to the battery modulewhen the temperature of the battery module becomes equal to or greaterthan the set temperature (T_(crit)).
 2. The battery pack systemaccording to claim 1, wherein each of the battery cells is aplate-shaped secondary battery.
 3. The battery pack system according toclaim 2, wherein the plate-shaped secondary battery is formed to have astructure in which an electrode assembly having acathode/separator/anode structure is mounted in a battery case formed ofa laminate sheet comprising a resin layer and a metal layer.
 4. Thebattery pack system according to claim 1, wherein the auxiliary powerunit is a low-capacity auxiliary battery or a capacitor.
 5. The batterypack system according to claim 4, wherein the capacity of the auxiliarybattery is 3 to 15% of that of the battery module.
 6. The battery packsystem according to claim 1, wherein the set temperature (T_(crit)) isset to a temperature range of −5° C. to 10° C.
 7. The battery packsystem according to claim 1, wherein the set temperature (T_(crit)) isset to a temperature range of 5° C. to 20° C. higher than a temperatureof 15° C. to 40° C. at which operation is properly performed.
 8. Thebattery pack system according to claim 1, wherein the charge anddischarge pulse current is a pulse wave current having the same chargeand discharge rate.
 9. The battery pack system according to claim 8,wherein the pulse wave current is a square wave type pulse wave currentor a sine wave type pulse wave current.
 10. The battery pack systemaccording to claim 1, wherein the charge and discharge pulse current issupplied at a ⅓ C-rate to 5 C-rate of each battery cell constituting thebattery module for 2 to 30 seconds.
 11. The battery pack systemaccording to claim 1, wherein the controller is an independent apparatusor is mounted in a battery management system (BMS).
 12. The battery packsystem according to claim 1, further comprising a bidirectionalconverter disposed between the battery module and the auxiliary powerunit to drive the charge and discharge pulse current.
 13. A devicecomprising the battery pack system according to claim 1 as a powersource.
 14. The device according to claim 13, wherein the device is anelectric vehicle, a hybrid electric vehicle or a plug-in hybrid electricvehicle.
 15. An operating method of the battery pack system according toclaim 1, the operating method comprising: (a) measuring the temperatureof the battery module before the battery module is electricallyconnected to the external device; (b) connecting the auxiliary powerunit to the battery module so that the charge and discharge pulsecurrent is supplied to the battery module when the measured temperature(T_(bat)) of the battery module is less than the set temperature(T_(crit)); (c) increasing the temperature of the battery moduleaccording to the supply of the charge and discharge pulse current to thebattery module; (d) interrupting the supply of the charge and dischargepulse current to the battery module when the temperature of the batterymodule is equal to or greater than the set temperature (T_(crit)); and(e) electrically connecting the battery module to the external device.16. The operating method according to claim 15, further comprisingcharging the auxiliary power unit before step (a) or step (b) or afterstep (e).
 17. The operating method according to claim 15, wherein theabove steps are performed immediately before the battery module isconnected to the external device to increase the temperature of thebattery module to a range of the set temperature (T_(crit)).
 18. Theoperating method according to claim 15, wherein the above steps arerepeatedly performed while the temperature of the battery modulecontinues to be monitored, in a state in which the external device isstopped (OFF), to maintain the temperature of the battery module at theset temperature (T_(crit)) or more.